A conventional automotive ignition system includes an ignition coil which powers a number of spark plugs so as to cause ionization between electrodes of each spark plug. The duration of ionization (referred to herein as "ionization time") is an important factor affecting engine efficiency, and it is usually desirable that the ionization time of each spark plug be substantially equal to the ionization time of every other spark plug in the engine, and also equal to a nominal ionization time.
A problem with conventional ignition systems is that they are usually insensitive to variables which can affect the ionization time of the spark plugs. For example, a change or error in the gap between a spark plug's electrodes can result in incorrect ionization time. Moreover, if the ionization time of one spark plug is greatly different from the ionization time of other spark plugs in the same engine, an imbalance occurs which reduces the efficiency of the engine. Changes in the characteristics of a conventional ignition coil can also result in improper ionization time for the spark plugs.
A related problem arises because such conventional systems operate with excess current dwell by saturating the ignition coil to ensure that the ignition system has enough energy to fire even fouled or mis-gapped spark plugs. This results in undesirably high power dissipation in the ignition coil, and particularly in the driver which supplies current to the ignition coil.
A further shortcoming of conventional ignition systems is their inability to detect, and alert the operator to, ignition system faults and/or spark plug faults which give rise to improper ionization times.